I use the Internet on my mobile for many tasks, including:
- Normal Email
- Read Headline News
- Read Breaking RSS News Feeds
- Check and Compare Prices when Shopping
- Download Maps (related to GPS)
- Read, Reply and Moderate Forums
- Monitor Server Stats
- Review Server Alerts (Exception Conditions)
- SSH into Server if Emergency
If there is a free WiFi hotspot in range, I use that; otherwise, I use GPRS.
I think I use my E61 for Internet much more than for actually talking on the phone or SMS! (FWIW: I also send between 200-300 SMS per month.)
Speaking of SMS, I get critical server alerts on my mobile via SMS using an email-to-SMS gateway.